• 대한산업공학회지
• /
• 제32권1호
• /
• pp.42-50
• /
• 2006

The multi-criteria group decision making (MCGDM) problem is to determine the best compromise solution in a set of competing alternatives that are evaluated under conflicting criteria by decision maker (DM)s. In this paper, we propose a mixed-integer programming (MIP) model to solve MCGDM. The existing method based on minimizing a distance measure such as Median Approach can not guarantee the best compromise solution because the element of median point vector is defined with respect to each criteria separately. However, by considering all criteria simultaneously, we generate median point that is better for locating the best compromise solution. We also utilize the concept of spatial dispersion index (SDI) to produce a threshold value, which is used as a guideline to choose either the Utopian Approach or the Median Approach. And we suggest using CBITP (Convex hull of individual maxima Based Interactive Tchebycheff Procedure) to provide DMs with various Pareto-optimal solutions so that DMs have broad range of selection.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 2001년도 추계학술대회 논문집
• /
• pp.21-24
• /
• 2001

This study is concerned with the development of efficient p-median approach to nondegenerate cell formation(CF) in group technology(GT) manufacturing. Unlike most of existing CF methodologies allowing degenerate cells or families that contains no parts or machines, this study attempts to find cell configuration where each machine cell contains at least two or more machines processing at least two or more parts so as to fully utilize the similarity in designing and processing parts. Nondegenerate CF seeks to minimize both the exceptional elements outside the diagonal block and the voids within the diagonal block. To find nondegenerate cells, a two-phase p-median methodology is proposed. In phase 1, the classical p-median model is implemented to find initial cells. In phase 2, bottleneck machines and parts are reassigned until no further degenerate cells and families are found. Test results on moderately medium-sized CF problems show the substantial efficiency of the proposed approach.

• 한국경영과학회:학술대회논문집
• /
• 대한산업공학회/한국경영과학회 2000년도 춘계공동학술대회 논문집
• /
• pp.40-43
• /
• 2000

This paper is concerned with development of an efficient Ρ-median approach applicable to large cell formation(CF) problems. A two-phase methodology that seeks to minimize the number of exceptional elements is proposed. In phase I, two efficient Ρ-median formulations which contain fewer binary variables than existing Ρ-median formulations are constructed. These make it possible to implement large CF problem within reasonable computer runtime with commercially available linear integer programming codes. Given the initial cell configuration found with the new p-median formulations, in phase II bottleneck machines and parts are reassigned to reduce the number of exceptional elements. This procedure has the flexibility to provide the cell designer with alternative solutions. Test results on large CF problems show a substantial efficiency of the new Ρ-median formulations.

• Journal of Chest Surgery
• /
• 제52권4호
• /
• pp.227-231
• /
• 2019

Background: There is no established surgical procedure for the treatment of epiphrenic esophageal diverticulum. The aim of this study was to compare the clinical outcomes of esophageal diverticulectomy using abdominal and thoracic approaches. Methods: We retrospectively reviewed 30 patients who underwent esophageal diverticulectomy through the thoracic or abdominal approach for an epiphrenic diverticulum at a single center between 1996 and 2018. We compared clinical outcomes, including the postoperative length of stay, time from the operation to oral feeding, leakage rate, and reoperation rate between the 2 groups. Results: The median age was 56 years. Of the 30 patients, 18 (60%) underwent diverticulectomy via the thoracic approach and 12 (40%) underwent the abdominal approach. The median hospital stay was 10 days (range, 5-211 days) in the thoracic approach group and 9.5 days (range, 5-18 days) in the abdominal approach group. The median time from the operation until oral feeding was 6.5 days (range, 3-299 days) when the thoracic approach was used and 5 days (range, 1-11 days) when the abdominal approach was used. In the thoracic approach group, the leakage rate was 16.67% and the reoperation rate was 27.78%. However, there were no cases of leakage or reoperation in the abdominal approach group. Conclusion: The abdominal approach for esophageal diverticulectomy is a feasible and appropriate alternative to the thoracic approach.

• 경영과학
• /
• 제24권1호
• /
• pp.91-111
• /
• 2007

In this paper an effective two-phase approach adopting modified p-median mathematical model is proposed for grouping machines and parts in cellular manufacturing(CM). Unlike the conventional methods allowing machines and parts to be improperly assigned to cells and families, the proposed approach seeks to find the proper block diagonal solution where all the machines and parts are properly assigned to their most associated cells and families in term of the actual machine processing and part moves. Phase 1 uses the modified p-median formulation adopting new inter-machine similarity coefficient based on the non-binary production data-based part-machine incidence matrix(PMIM) that reflects both the operation sequences and production volumes for the parts to find machine cells. Phase 2 apollos iterative reassignment procedure to minimize inter-cell part moves and maximize within-cell machine utilization by reassigning improperly assigned machines and parts to their most associated cells and families. Computational experience with the data sets available on literature shows the proposed approach yields good-quality proper block diagonal solution.

• Journal of the Korean Statistical Society
• /
• 제22권1호
• /
• pp.1-12
• /
• 1993

An approach to make the information bound sharper in median-unbiased estimation, based on an analogue of the Cramer-Rao inequality developed by Sung et al. (1990), is introduced for continuous densities with a nuisance parameter by considering information quantities contained both in the parametric function of interest and in the nuisance parameter in a linear fashion. This approach is comparable to that of improving the information bound in mean-unbiased estimation for the case of two unknown parameters. Computation of an optimal weight corresponding to the nuisance parameter is also considered.

• 대한산업공학회지
• /
• 제38권1호
• /
• pp.57-66
• /
• 2012

The paper deals with the development of a model for group decision making under multiple criteria. The Multi-criteria group decision making (MCGDM) is the process to determine the best compromise solution in a set of competing alternatives that are evaluated by decision makers having their own preferences on conflicting objectives. For MCGDM, we propose a Mixed-Integer Programming (MIP) model that implements a revised median approach by noticing that the original median approach cannot consider the willingness to reject and the indifferent preference conditions. The proposed MIP model tries to select a common best Pareto-optimal solution by maximizing the overall desirability considering the willingness to reject and the indifferent preference that represent the tolerance measure of each decision maker. To evaluate the effectiveness of the proposed model, we compared the results of the proposed model with those of the median approach. The results showed that the proposed MIP model produces more realistic and better compromised alternative by incorporating the decision maker's willingness to reject and the indifferent preferences over each criteria.

• Nuclear Engineering and Technology
• /
• 제54권9호
• /
• pp.3380-3389
• /
• 2022

We evaluated the performance of an improved hybrid median filter (IHMF) applied to X-ray computed tomography (CT) images obtained using a high-resolution photon-counting cadmium zinc telluride (CZT) detector. To study how the proposed approach improves the image quality, we measured the noise levels and the overall CT-image quality. We established a CZT imaging system with a detector length of 5.12 cm and thickness of 0.3 cm and acquired phantom images. To evaluate the efficacy of the proposed filter, we first modeled two conventional median filters. Subsequently, we were able to achieve a normalized noise power spectrum result of ~10^-8 mm², and furthermore, the proposed method improved the contrast-to-noise ratio by a factor of ~1.51 and the coefficient of variation by 1.55 relative to the counterpart values of the no-filter image. In addition, the IHMF exhibited the best performance among the three filters considered as regards the peak signal-to-noise ratio and no-reference-based image-quality evaluation parameters. Thus, our results demonstrate that the IHMF approach provides a superior image performance over conventional median filtering methods when applied to actual CZT X-ray CT images.

• Journal of Chest Surgery
• /
• 제49권5호
• /
• pp.356-360
• /
• 2016

Background: The standard approach in treating cardiac myxoma is the median full sternotomy. With the evolution of surgical techniques, the right minithoracotomy approach has emerged as an alternative method. Since few studies have been published assessing the right minithoracotomy approach, we performed a retrospective study to compare the clinical outcomes of the right minithoracotomy approach with those of the sternotomy approach. Methods: From January 2005 to December 2014, 203 patients underwent resection of a cardiac myxoma. Patients with preexisting cardiac problems were excluded from this study. 146 patients were enrolled in this study; 83 patients were treated using a median sternotomy and 63 patients were treated using a right minithoracotomy. Results: No early mortalities were recorded in either group. Although the cardiopulmonary bypass time and aorta cross-clamp time were significantly shorter in the sternotomy group (p<0.001 and p=0.005), postoperative blood transfusions and arrhythmia events were significantly less common in the thoracotomy group (p=0.004 and p=0.025, respectively). No significant differences were found in the duration of the hospital stay, postoperative intubation time, the duration of the intensive care unit stay, and recurrence. Conclusion: The minimally invasive right minithoracotomy approach is a good alternative method for treating cardiac myxoma because it was found to be associated with a lower incidence of postoperative complications and a shorter postoperative recovery period.

• 한국건설관리학회논문집
• /
• 제9권1호
• /
• pp.143-154
• /
• 2008

다양한 제반 위험요소가 상존하는 고속도로 교통안전시설의 안전에 대한 사회적 관심증가로 인하여 교통안전시 설에 대한 체계적인 성능, 비용 및 효과 분석 프로세스가 요구되어지고 있다. 교통안전시설은 도로사용자의 직 간접적인 사고위험성이 상존하는 중요한 시설물임을 고려하여 위험도의 정량적 평가에 대한 고려가 필수적이다. 본 연구에서는 교통안전시설의 가치분석 수행시 정량적 위험도분석 결과를 적용한 합리적인 가치분석(VE)기법을 제시하였으며, 고속도로 개선 전 후 중앙분리대에 적용하여 가치평가를 수행하였다. 또한 기능분석을 통해 중점개선대상 기능 도출기법을 제시하였으며, 이를 통해 개선 전 중앙분리대 문제점의 정확한 분석이 가능하며 향후 다양한 교통안전시설의 가치대안 창출 시 적용 가능하다.